Open Stack

Hi everyone,

I have a change submitted that lays the groundwork for using custom enums and fields that are used by versioned objects [1]. These custom fields allow for verification on a set of valid values, which prevents the field from being mistakenly set to something invalid. These custom fields are best suited for StringFields that are only assigned certain exact strings (such as a status, format, or type). Some examples for Nova: PciDevice.status, ImageMetaProps.hw_scsi_model, and BlockDeviceMapping.source_type.

These new enums (that are consumed by the fields) are also great for centralizing constants for hard-coded strings throughout the code. For example (using [1]):

Instead of
    if backup.status == ‘creating’:
        <do_stuff>

We now have
    if backup.status == fields.BackupStatus.CREATING:
        <do_stuff>

Granted, this causes a lot of brainless line changes that make for a lot of +/-, but it centralizes a lot. In changes like this, I hope I found all of the occurrences of the different backup statuses, but GitHub search and grep can only do so much. If it turns out this gets in and I missed a string or two, it’s not the end of the world, just push up a follow-up patch to fix up the missed strings. That part of the review is not affected in any way by the RPC/object versioning.

Speaking of object versioning, notice in cinder/objects/backup.py the version was updated to appropriate the new field type. The underlying data passed over RPC has not changed, but this is done for compatibility with older versions that may not have obeyed the set of valid values.

[1] https://review.openstack.org/#/c/256737/


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Thanks,

Ryan Rossiter (rlrossit)